A Shrinking Core Model Approach to Designing a Natural Gas Desulphurization Unit

Sulfur compounds especially H2S should be safely removed from the natural gas.
Known as one of the major environmental hazards, H2S is undesirable because of its
toxicity in nature. The sulfur compounds can be poison to human health through several
routes including by ingestion, intravenous and intraperitoneol. It can cause irritant to
eyes, respiratory system and skin. In an industry, process for desulphurizing is required
as traces of sulfur compounds can corrode equipments and poison other metal catalysts.
Hence, desulphurization column is highly necessary to be used in industry to remove
sulfur compounds to as low as 1 ppm. However, problems occur as there is insufficient
of simple methodology in designing the desulphurization column systematically. Thus,
aim of the project is to provide an efficient and simple methodology and framework in
designing the desulphurization column by using shrinking core model approach. Noncatalytic
gas solid reaction between ZnO which act as an adsorbent and H2S was
studied. The results show that the kinetic behaviors of the reaction can be described by
an improved shrinking core model. An analysis on H2S concentration, radius of
adsorbent and temperature of reaction has been made to observe the effects of these
factors on desulphurization and adsorption capacity. Application of the model is
performed by using existing fertilizer data. It is found that the breakthrough or service
time for a single pellet of ZnO adsorbent with a radius of 2mm at 673K and 43atm is
66.8 min. By using a simple and proper scale up technique, the desulphurization column
has been designed. Reasonable dimensions of the desulphurization column show that the
improved shrinking core model can be used for the industrial usage. Comparison of
dimensions of the desulphurization column between results from improved shrinking
core model and existent desulphurization column gave very low sums of squares error
which is 0.0028. It is noted that the desulphurization column can be designed by taking
a basis of a single pellet and scale it up to a column.